Many data processing and computing environments require that user data be kept securely away from those who should not know, or might otherwise misuse such data. Such sensitive information might relate to national security, consumer creditworthiness, or the grades to be given to high school students. Doctors and lawyers need to secure their files from those who might otherwise seek access to privileged information.
At the same time, there is a continuing need on the part of computer users to have access to vast quantities of stored information on a random access basis and at very high access speeds. While removable floppy disks provide random access to stored user data, such disks provide access relatively slowly. With much faster access and greater storage capacities than floppies, Winchester fixed disk drive storage systems have come into widespread within computing environments, including small, portable single user workstations and personal computer systems.
Physically small computer systems are proliferating throughout all walks of life, and such systems are being applied to a virtually unlimited variety of tasks and within untold environments. These small, often portable computing systems have evolved into a generally standard variety of sizes and shapes, and have come to recognize as a "form factor" standard the height, width and depth constraints of the ubiquitous 51/4 inch "half height" floppy disk drive. The front panel recess (called a "disk drive bay") formed within these small computers is uniformly sized and configured to receive the full height or more recently the half height floppy disk drive. Typical dimensions for a 51/4 inch diameter, half height disk drive, whether floppy or hard, are 53/4 inches wide, 15/8 inches high, and 8 inches deep.
One recognized drawback of small computing systems is the relative difficulty in securing all of the data stored and used in conjunction with such small systems. This difficulty has required that the premises containing the system be secured against all intrusion. Such is not practical in large office buildings where janatorial workers and maintenance personnel require access during evening and weekend hours when the office is closed.
While some smaller data bases and files may be contained on and used with one or a few floppy disks which may be removed from the computer and placed in a safe at night, most present computer programs and related applications files are so large as not to fit within the capacity of the floppy disk. It is very time consuming to transfer large files from large capacity hard disk drives to a number of floppy disks, and then erase the large files from the hard disks, merely to secure the data at the end of each work day, and then to reload the large files from floppy disks in order to begin work the next day. Also, it is not efficient to lock the entire computer within a safe at night.
Another heretofore unsolved need has been to provide a convenient way to enable a personally configured hard disk based operating environment to accompany the user from computer to computer, including providing an operating system bridge, from such operating systems as DOS to 0/S 2 and back, and from such computing systems as the IBM Personal Computer AT to and from the IBM Personal Computer P/S 2, for example.
Thus, a need has arisen for a practical way to provide the storage capacity and fast data access and transfer rates of a compact, ruggedized hard disk drive subsystem with the portability and securability of a floppy disk in a "form factor" not any larger than occupied by the standard half 1 height floppy disk drive form.
The assignee of the present invention has pioneered the introduction and widespread market acceptance of the micro-Winchester disk-on-a-card concept, sold under the HARDCARD trademark, and has patented that concept in U.S. Pat. No. 4,639,863. Modular unitary disk file subsystems as taught in that patent have worked very well as data transporters, i.e., they may be readily installed and removed and placed in a safe by the user at night, for example, without need for special tools or any cabling whatsoever. IBM proposed a similar modular plug-in floppy disk drive subsystem in an article entitled "Diskette Drive Single Connector Low Power Interface" appearing in the IBM Technical Disclosure Bulletin, Vol. 28, No. 9, Feb. 1986, pp. 3877-3878.
One inconvenience in using the disk-on-a-card subsystems as securable/transportable high capacity data storage devices is the need to open, or actually remove the computer cabinet in order to insert and remove the hard-disk-on-a-card to and from its plug-in attachment to the motherboard socket or backplane. Also, the edge connector traces and their plugs are not designed or intended for many insertions and removals.
Heretofore, it has been thought that the task of providing adequate shock mounting for a micro-Winchester (31/2 inch disk diameter) head and disk assembly for use within a portable computer environment has required at least the volume of space occupied by a conventional 51/2 inch half height floppy disk drive, or a larger space. One representative teaching following this thinking is to be found in the McGinlay et al. U.S. Pat. No. 4,568,988, assigned to Rodime PLC, Glenrothes, Scotland (see FIG. 6 and the discussion in connection therewith).
Other manufacturers have proposed portable Winchester hard disk modules. One manufacturer of a hard disk module for use with a personal computer is Tandon Computer Corporation, 405 Science Drive, Moorpark, California 93021. Tandon has developed a product known as the "Personal Data Pac" which includes a 30 Megabyte RLL formatted micro-Winchester hard disk within a plug-in module. However, that product is consistent with the teaching of the McGinlay et al patent, in that it employs a "stepper motor like" interface with the disk drive controller and in that it has not been effectively size-reduced so as to provide a shock resistant micro-Winchester module which may be plugged into a base unit which itself fits entirely within the recess form factor provided for the standard half height floppy disk. Thus, the Tandon Personal Data Pac product has required an external base unit and exposed cables in order to attach to and be used with conventionally sized personal computers. A similar, cable-connected, external base unit product, known as the "Datamodule" is being offered by Inmao, 470 Mercury Drive, Sunnyvale, Cal.
Another manufacturer of another proposed micro-Winchester-based fixed disk module is JVC Information Products Company of America, 1011 West Artesia Blvd., Compton, CA 90220. The JVC product proposed an enclosed head and disk assembly, either type JD-3824R or JD-3812M Series, which plugged into a base housing containing control and interface electronics. A ruggedized "suitcase" type carrying case was proposed in commercial literature for transporting the head and disk assembly.
There are several rigid disk cartridge based products which will plug into base units occupying standard floppy disk drive half height form factors. One such product is made by Syquest Technology, 47923 Warm Springs Blvd., Fremont, Cal. 94539 under the model number SQ312RD. A plated, rigid disk is rotatably contained within a plastic cartridge, model number SQ200, which is received within a base unit containing a spindle motor and a head assembly and actuator.
The problems associated with cartridge-type products are the same difficulties long associated with disk packs, namely, disk spindle rotational eccentricities which vary from base unit to base unit, and the non-trivial task of purging impurities from the disk cartridge which otherwise come between the low flying head and the disk surface. A similar product, Model 360, was announced by DMA Systems, Goleta, California, in an article written by David Sutton, entitled "Removable Cartridge Winchester Triples Performance-To-Volume Ratio" appearing in Mini Micro Systems magazine, March, 1984 issue, pages 245, 246, and 248.
Another removable disk cartridge is the "Bernoulli Box" product line offered by Iomega Corporation of Ogden, Utah, as generally depicted and discussed in U.S. Pat. No. 4,458,273, for example. This product supports a floppy disk upon a Bernoulli plate within a cartridge and thereby enables use of flying head technology. Another disk cartridge concept is presented in an article by Hatchett entitled "Dual-Use Data Cartridge" in the IBM Technical Disclosure Bulletin, Vol. 23, No. 4, September 1980, pages 1652 and 1653. The problems associated with disk cartridges discussed above in conjunction with the Syquest product and with the DMA Systems product are also presented with the disk cartridge approach to mass storage.